To restart the Instant Outliner, I needed the equivalent of FriendFeed's realtime update functionality.
It's really elegant, but I couldn't make my software depend on another service for update notification. I started to do it in REST and realized that I was reinventing a lot of what XML-RPC already did.
A day later I had it working and a day after that I had the Instant Outliner converted. Unlike previous implementations this one works perfectly, is instantaneous and requires no polling. The long-poll approach works perfectly.
I wanted to document this for the programmers who are testing the Instant Outliner, because the realtime updating functionality is more general, it can be used to connect our workgroup together in more ways than through I/Oing.
There are two entry-points, one to get the next set of updates, and one to push an update to the workgroup. Both assume there's an identity system in place that can independently determine if a username/password is valid. (The identity function hooks in as a callback.)
You can find the source for both the client and the server at builtins.realtime in opml.root.